This is the color combination that I tend to repeat most often: purple and lime green. Here I did it with Geranium "Rozanne", a perennial that is hardy to zone 5, likes partial to full sun, and blooms all season long. For the lime green I used Sweet Potato Vine "Margarita", an annual that is well worth buying every year because of its fantastic trailing habit. (For more evidence, check out my link from last August.) To the right of the picture, you'll see a bronze colored leaf as well. That's from Sweet Potato Vine "Sweet Caroline".
Feel free to comment with color combinations that you like to put together. I'm always looking for new ideas.